The present invention relates to a magnification selecting device, more particularly, to a magnification selecting device which is capable of continuously varying magnifications by operating either UP key or DOWN key.
A prior art presents in its Japanese Patent Laid Open Publication No. 220772 of 1984 a mechanism related to the image generating apparatus such as an electrophotographic copying machine, which is provided with the UP and DOWN keys for finely selecting magnifications so that the magnification can continuously be increased or decreased by selectively operating either of these keys. This apparatus is also provided with the stationary magnification key for selecting any of those magnifications which are frequently made available for either enlarging or reducing between papers of stationary sizes so that any desired magnification can easily be selected by operating any of the stationary magnification keys.
Since the image generating apparatus mentioned above is provided with the stationary magnification keys in addition to the UP and DOWN keys, operational characteristic can certainly be improved. On the other hand, unless the number of keys on the operation panel is minimized, operation of other keys including an effort for finding the keys to be operated unavoidably involves complexity to conversely lower the total operational characteristics. As a result, the kind of stationary magnification key should be minimized. If the kind and number of the stationary magnification keys were minimized, there will be a number of such stationary magnifications that cannot be accessed by operation of the stationary magnification keys, which any of these stationary magnifications should carefully be selected by operating either of the UP and DOWN keys.
When selecting the desired magnification by operating either of the UP and DOWN keys, since the conventional apparatus allows the UP and DOWN keys to set minimum of 64% through a maximum of 141% by 1% graduation, when varying magnifications by operating either of these UP and DOWN keys, magnification varies itself at a considerably fast speed like 8 milliseconds/% for example, and as a result, it is extremely difficult for the operator to precisely control the timing to stop the operation of either of these UP and DOWN keys while watching the magnification display. Actually, the desired magnification is easily passed when the key operation is stopped. To correctly set the magnification to the desired value, the operator is obliged to repeat operations of the UP and DOWN keys many times, thus eventually resulting in the poor operational characteristic for correctly selecting the aimed magnification.
In addition, when operating the copying machine for generating picture image by using a stationary magnification, a certain amount of blank portion may have to be provided in the edge portion of the generated image. When this is actually needed, after selecting the desired magnification by operating one of the stationary magnification key, the operator is then obliged to diminish the magnification by several percents by operating the DOWN key, thus unavoidably facing poor operational characteristic for selecting the aimed magnification as mentioned above.